1. Field of the Invention
The present invention relates to a battery pack to be mounted in a vehicle, and more particularly to the position of a relay to be housed in the battery pack.
2. Description of the Related Art
Heretofore, hybrid electric vehicles and fuel cell vehicles as well as electric vehicles were equipped with a battery pack for storing electric power to supply a drive motor. The battery pack includes a battery stack formed by combining multiple battery modules, various devices to control the battery stack, and an upper case and a lower case to protect the battery stack and the various devices. One example of the various devices disclosed in Japanese Patent Laid-Open Publication No. 2005-328597 is a relay for disconnecting as necessary the electric power that is supplied from the battery stack to the drive motor.
FIGS. 6A, 6B, and 6C illustrate the operating principle of the relay. A relay 1 is, for example, attached to a top of a bottom face 14a of a lower case 14 by a mounting screw 2a via a fixture 2. The relay 1 is a so-called mechanical relay and has an excitation coil 1a, a movable core (drive shaft) 1b that moves by electromagnetic force of the excitation coil 1a, and a case 1d for storing the excitation coil 1a, the movable core 1b, and so forth.
In FIG. 6A, when the relay 1 turns on, the excitation coil 1a is energized to generate electromagnetic force. As a result, as shown in FIG. 6B, the movable core 1b rises, a return spring 1e is compressed, and an internal contact terminal 1c provided on the top of the movable core 1b contacts an external input terminal 3a and external output terminal 3b so that the external input terminal 3a and the external output terminal 3b are electrically connected via the internal contact terminal 1c. Furthermore, when the relay 1 turns off, the electromagnetic force of the excitation coil 1a dissipates, the movable core 1b falls due to the return force of the contracted return spring 1e, and the internal contact terminal 1c separates from the external input terminal 3a and the external output terminal 3b so that the external input terminal 3a and the external output terminal 3b are electrically disconnected.
When the relay 1 changes from the on state to the off state, as shown in FIG. 6C, the movable core 1b impacts the bottom face of the case 1d due to the return force of the return spring 1e and the impact vibrations are transmitted to the entire relay 1. The impact vibrations are transmitted to the lower case 14 via the mounting point 2b and may vibrate the battery pack to generate noise.
The quietness of equipment mounted in a vehicle is an important factor on which the product value of the equipment can be judged. Thus, it is preferable for the impact sound generated from the relay provided in the battery pack to be dampened.
Heretofore, to dampen the shock generated during the sliding operation of the movable core 1b, dampening was applied by attaching the relay 1 and the fixture 2 via a shock absorbing member 4 (rubber cushion).